According to a study published by JAMA, a high daily dose of vitamin D does not lower the risk of wintertime upper respiratory tract infections in young children. The research showed almost no difference in the amount of infections suffered by children who received a higher dose of vitamin D and those who received a standard dose.
Viral upper respiratory tract infections such as the common cold and flu are the most prevalent infectious illnesses of childhood. Previous research indicated a link between low levels of serum 25-hydroxyvitamin D and increased rates of respiratory tract infections. Dr. Jonathan L. Maguire of the University of Toronto led a team of colleagues in testing this theory.
Young children between the ages of 1 and 5 were randomly assigned to receive a high dose of 2,000 IU/d of vitamin D or a standard dose of 400 IU/d of vitamin D. The supplements were given for a minimum of four months between September and May.
Nasal swabs of the children were tested for infection and revealed little difference in the outcomes of the two groups. For example, the average number of upper respiratory tract infections were 1.05 for the group that received high doses of vitamin D and 1.03 for the group that received standard doses of vitamin D.
The results of the study also showed no significant difference in the average amount of time until the first lab-confirmed infection, with 3.95 months for the high-dose group and 3.29 months for the standard-dose group. The number of parent-reported infections for both groups was very similar as well.
The authors pointed out that one limitation of the study is that some of the children may have experienced upper respiratory infections that were not documented. Nonetheless, the authors wrote that the “findings do not support the routine use of high-dose vitamin D supplementation in children for the prevention of viral upper respiratory tract infections.”